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Supporting Information

Metal Free Carbon as a Catalyst for Oxidative Coupling: Solvent Enhance Poly-Coupling with Regioselectivity

Melad Shaikha, Aanchal Sahua, Atyum Kiran Kumarb Mahendra Sahua, S. K. Singha and Kalluri V.S. Ranganath*a

a Guru Ghasidas University, Bilaspur-495009, India, E-mail: rangakvs1@gmail.comb Dept. of Materials Science and Engineering, RGUKT, Basar-504101, India.

Contents for the supporting information

Entry Contents Page No

1 Experimental procedure S2

2 Mechanism S4

3 FTIR of naphthol polymer S5

4 TG-TDA of naphthol polymer S6

5 FTIR of Graphene oxide S7

6 PXRD of Graphene oxide S7

7 XPS of GO S8

8 NMR spectras S9-S15

Electronic Supplementary Material (ESI) for Green Chemistry.This journal is © The Royal Society of Chemistry 2017

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1. Experimental Section

1.1 Experimental procedure for the synthesis of graphene oxide:

Graphene oxide (GO) was synthesized from Graphite flake by the oxidation processes reported by the

modified Hummers method using KMnO4 and H2SO4 as the oxidizing agents. (W. S. Hummers, R. E.

Offeman, J. Am. Chem. Soc., 1958, 80, 1339). In this method, the 9:1 (v/v) mixture of concentrated

H2SO4/H3PO4 (360:40 mL) was added to a mixture of graphite flake (3.0 g) and KMnO4 (18.0 g),

produced a slight exothermic to 40°C. The mixture was then heated to 50°C and stirred for 12h. After

cool down to room temperature, the mixture was poured into a beaker containing 400 gram of ice and

15 ml of H2O2 (30%) and stirred till the colour changes from dark violet to orange-yellow. Then the

mixture was centrifuged and the supernatant was removed. For purification, the product was washed

5−7 times with 5% (v/v) HCl solution followed by deionized H2O and 200 mL of ethanol. The

synthesised solid obtained on the filter was vacuum-dried overnight at room temperature.

1.2 Experimental procedure for the oxidative coupling of 2-naphthols (in toluene):

In a round bottomed flask containing, 2-napthols (2.0 mmol) and Graphene oxide (20 mg) in

toluene (5.0 mL) was added NaOH (20 mg, 0.5 mmol). The resulting mixture was stirred at

100 °C for 12 h. After completion of the reaction, GO was separated through filtration. To the

reaction mixture was added ethyl acetate (3x 10 ml) and saturated aqueous solution of NaCl

(10 mL). Later dil. HCl was added slowly till the solution is neutralized. The combined

organic layers were passed through charcoal and dried over anhydrous Na2SO4. The resulting

residue was then purified by silica (60-200 mesh) column chromatography using petroleum

ether and ethyl acetate (15%, v/v) as an eluent.

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1.3 Experimental procedure for the oxidative coupling of 2-naphthols (in water):

In a round bottomed flask containing, 2-napthols (2.0 mmol) and GO (20 mg) in water (5.0

mL) was added NaOH (20 mg, 0.5 mmol). The resulting mixture was stirred at 100 °C for 12

h. After completion of the reaction, GO was separated through filtration. To the reaction

mixture was added ethyl acetate (3x 10 ml) and saturated aqueous solution of NaCl (10 mL).

Later dil. HCl was added slowly till the solution is neutralized. The combined organic layers

were passed through charcoal and dried over anhydrous Na2SO4.

(Note: The GO was separated through filtration under hot conditions to get the clear solution. To the clear solution, ethyl acetate was added followed by saturated sodium chloride and required amount of dil. HCl. The formation of white precipitation was observed in aqueous layer and unreacted materials are in the organic layer and thus the naphthol polymer was separated by simple filtration and washed several times with water and dried at 60 ⁰C as shown in the following scheme S1).

Scheme S1. Pictorial representation for separation technique of naphthol polymer

Table S1: Oxidative coupling of 2-naphthols in polar solvents using GO as catalyst

S.no Solvent Conv.(%) Homo coupling product Poly coupling product

1 Water 88.6 - Polymeric material was isolated

2 DMF 9.8 6 -

3 DMSO 15.6 10 -

aAll reactions were carried out using 20 mg of catalyst, solvent (5.0 mL), reactant (2.0 mmol), NaOH (20.0 mg)

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2. Plausible Mechanism for Oxidative Coupling/Poly-coupling:

The plausible mechanism for the oxidative coupling of 2-naphthol to BINOL is shown

in the Scheme S2. The OH- ion of sodium hydroxide can interact with OH group of the

2-naphthol to form 2-naphthalenolate. It has been reported that the active radical

species is generated by C=C groups of GO and in the present case, possibly involved

with the single electron transfer mechanism. The 2-naphthalenolate has been transfer

single electron to C=C of GO and form 2-naphthyloxyl radical. The radical is in

resonance to C-1 position of 2-naphthol and thus the preferential formation of the

diketone intermediatea through dimerization of a C-1 radical. Thus generated 2-

naphthoxyl radical and the diketone intermediate rapidly produce the BINOL through

rearomatizing enolization.b Similarly, the polymer is produced through the radical

generation, dimerization, termination of polymer formation by 2-naphthyloxyl radical

and keto-enol isomerization of the C-3 position of dimer BINOL.

O

OH

OH

O

COOH

HOOC

O

OH O-O

OH

OH

O

COOH

HOOC

OO.

.(-)

NaOH

Graphene oxide Graphene oxide(radical formation)

O.

OO

OHOH

H

H

dimerization

isomerization

keto-enol

NaOH

radical formation

Graphene oxideOO

.

polymerization

OO

..

.

OO

OO

OO

H

H

H

H

..

n

OHOH

HOHO

HOHO

n

isomerization

keto-enol

OO

OO

OO

H

H

H

H

n

O

O

H

H

H

H

HO

HO

O.

chain termination

Scheme S2. Plausible mechanisms for the oxidative coupling of 2-naphthol using GO

((a) Y. Koyama, S. Hiroto, H. Shinokubo, Angew. Chem. Int. Ed., 2013, 52, 5740-5743. (b) T. Matsuno, Y. Koyama, S. Hiroto, J. Kumar, T. Kawai, H. Shinokubo, Chem. Commun., 2015, 51, 4607-4610; (c) X. Li, J. B. Hewgley, C. A. Mulrooney, J. Yang and M. C. Kozlowski, J. Org. Chem., 2003, 68, 5500-5511; (d) S. Habaue, T. Temma, Y. Sugiyama, P. Yan, Tetrahedron Lett., 2007, 48, 8595-

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8598; (e) Q. –X. Guo, Z. –J. Wu, Z. –B. Luo, Q. –Z. Liu, J. –L. Ye, S. –W. Luo, L. –F. Cun and L. –Z. Gong, J. Am. Chem. Soc., 2007, 129, 13927-13938; (f) M. Matsushita, K. Kamata, K. Yamaguchi, N. Mizuno, J. Am. Chem. Soc., 2005, 127, 6632-6640.)

3. FTIR of naphthol polymer.

Fig. S1. FTIR of naphthol polymer

Table S2 FTIR analysis of naphthol polymer

Entry Absorbance (cm-1) Vibration assignments

1 3447.68 Broad peak, reveal O-H stretching

2 2955.00 Aromatic C-H vibration

3 1653.98, 1421.82 C=C stretching in aromatic nuclei

4 1088.48 Presence of C-O stretching for C-O-H

5 797.23 aromatic C-H out of plane bending vibration

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4. TG-DTA of naphthol polymers.

Fig. S2 TG-DTA of (a) naphthol polymer, (b) 6-MeO-2-naphthol polymer and (c) 6-Br-2-naphthol polymer

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5. FTIR of Graphene oxide.

Fig. S3 FTIR spectra of a) freshly prepared GO b) after recycling of GO from the oxidative coupling.

6. PXRD of graphene oxide.

Fig. S4 PXRD pattern of (a) Graphite and (b) prepared GO.

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7.1 O 1s XPS of graphene oxide.

Fig. S5 O1s of XPS spectra of GO.

7.2 XPS scan survey of graphene oxide.

Fig. S6 Surface Scan Survey of XPS spectra

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8. NMR of BINOL derivative

Fig. S7 1H-NMR of 2,2’-dihydroxy-1,1’-binaphthol (BINOL)

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Fig. S8 1H-NMR of 6,6’-dibromo-2,2’-dihydroxy-1,1’-binaphthol.

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Fig. S9 1H-NMR of 6,6'-dimethoxy-[1,1'-binaphthalene]-2,2'-diol.

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Fig. S10 1H-NMR of 3,3'-diamino-[1,1'-binaphthalene]-2,2'-diol.

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Fig. S11 1H-NMR of 2,2'-dihydroxy-[1,1'-binaphthalene]-6,6'-dicarbonitrile.

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Fig. S12 1H-NMR of 7,7’-dibromo-2,2’-dihydroxy-1,1’-binaphthol

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Fig. S13 1H-NMR of [9,9'-biphenanthrene]-10,10'-diol